Saturday, November 19, 2011

[solved] naxa nmv-155 sized playback (QVGA)

Let's see if we can get anywhere with this inexpensive media player. I find players like these NAXA's in bargain bins for $15, (probably $5 worth of parts in the unit), but the day I wanted to toy with one, I was only able to find one as cheap as $25. Bought it anyway.

In forums about these knock-off players, the two most common problems are USB recognition and media formatting. It's got a 4GB internal, and room for a card as well. But it's picky about file formats... it's cheap. Secondly, I was excited to read in its manual, that the NAXA can display PDF's (Edit: this was misadvertised; it reads only basic text files), in addition to MP3's, movies, and photos. Battery life is reasonable.


Unit comes without any cover but fits into a G1 holder (remaining after I had a G1 stolen). A USB -> micro-USB connector cable, a 300mA AC->micro-USB charger, earbuds, stylus (a plastic dental pick also works), Windows disk, and a small manual.

USB detection/connection

Threw out the Windows disk and plugged in the USB, and no auto-recognition took place in any file managers. Nothing in lsusb. Seeing nothing in udevmonitor either, I swapped USB cables with a known good USB cable (for a different device) and suddenly the NAXA appears in the file manager, no problems. It's identified there as "GENERIC USB DISK DEVICE Music Player" (3.5GB). We're already at less than the advertised 4GB. In lsusb, it appears as
10d6:1101 Actions Semiconductor Co., Ltd D-Wave 2GB MP4 Player / AK1025 MP3/MP4 Player
This 2GB reading is probably the most accurate -- I've likely been ripped off: appears I have a Chinese 2GB device hacked to indicate twice its real capacity. Happens. A different system check (below) shows 3.7 GB, but I'd bet against it and with the 2GB reading.
# df
/dev/sdc 3709840 2084 3707756 1% /media/disk
Summary: Ditch the included USB->micro-USB cable and the Windows disk. Storage expectations should be reduced to a little less than 2GB for this (likely) piece of shiat.


Let's upload something less than 2GB and see if it plays.
  • MKV - First-up, a 1.4GB sports vid coded in MKV. Result: the file is not even detected in the device file manager. Can't even be seen there.
  • AVI - Second, we'll do a standard AVI, let's go. Here's the encoding and resolution
    Stream #0.0: Video: mpeg4, yuv420p, 608x336
    Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 96 kb/s
    This file appeared in the device. I attempted to play it, but the NAXA displayed a "file format error".

QVGA = 320x240

Next step: record a short vid on the device, make sure it plays on the device (it did), and then download to the laptop and determine its settings and codecs.
Duration: 00:00:17.93, start: 0.000000, bitrate: 551 kb/s
Stream #0.0: Video: mpeg4, yuv420p, 320x240
Stream #0.1: Audio: mp3, 16000 Hz, stereo, s16, 64 kb/s
So 320x240 (ie, QVGA) and 551k bitrate, and only 64 k on the sound. This is what the NAXA makes and plays.

Let's approximate that. I'll take a file taxi_s01e01.avi and, not worrying about B frames or whatever, split it into audio and video, and then render it back together, but in QVGA with MP3:
$ ffmpeg -i taxi_s01e01.avi -vn -ar 44100 -ac 2 s1e1.wav
$ ffmpeg -i taxi_s01e01.avi -vcodec libxvid -b:v 500k -s qvga -an s1e1.avi
$ ffmpeg -i s1e1.avi -i s1e1.wav -acodec libmp3lame
-ar 44100 -ab 192k -ac 2 -vol 330 -vcodec copy -b:v 504k qvga_taxi_s01e01.avi
This encoded without errors and played without errors.

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